New York had back-to-back homers for the third consecutive game and has 13 back-to-back homers this season.
Posada had two RBI for the Yankees, who have won eight of their last nine games. Johnny Damon was 3-for-5 with a pair of doubles and an RBI and Melky Cabrera had two RBI.
David Robertson (2-1) earned the win after recording the final out in the eighth. New York starter Joba Chamberlain gave up four runs on five hits in six innings.
Lyle Overbay had three RBI and Edwin Encarnacion and Randy Ruiz, who had his contract selected from Triple-A Las Vegas prior to the game, both had solo homers for the Blue Jays.
Jesse Carlson (1-5) suffered the loss, giving up three runs in just 1/3 inning in relief.